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• 60 Let $k$ be a natural number . Then $3k+1$ , $4k+1$ and $6k+1$ cannot all be square numbers.
• 10 How to prove $\frac xy + \frac yx \ge 2$
• 10 What are the steps to solve this limit $\lim _{x\to 0} \frac{\cos(x+\pi/2)}x$?
• 9 Solve $(x-2)^6+(x-4)^6=64$ using a substitution.
• 9 Solve $2^x+4^x=2$
• 8 How to integrate $xe^x$ without using antiderivatives or integration by parts.
• 8 Re-write a quadratic equation in another form?
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